Alpha-linolenic acid (ALA) is a short-chain omega-3 fatty acid found primarily in plants. ALA is an essential fatty acid (EFA), meaning the body cannot synthesize it and it must be consumed in the diet. Foods high in ALA include various nuts/seeds and their oils, such as walnuts, flaxseed, hemp seeds, chia seeds, and canola oil.^[3] Smaller amounts can be found in kiwi fruit, spinach, watercress, and grass-fed beef.^[4][5] ALA consists of an 18-carbon chain with three double bonds, making it a polyunsaturated fatty acid. Within the body, ALA can have many functions. It can be broken down for energy via the β-oxidation metabolic pathway; be incorporated into cell membranes, affecting their fluidity and cell signaling; influence gene expression; and be metabolized into other bioactive compounds, such as oxylipins (chemical messengers) or other omega-3 fatty acids such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), although this occurs at a low rate.^[6] While both DHA and EPA (primarily found in fish oil) have many reported health benefits, the effects of ALA are less clear.

ALA may have small cardiovascular benefits, but the research is fairly mixed. In short-term trials (2–3 months), ALA seems to minorly reduce triglyercides (although less efficiently than fish oil), LDL-cholesterol, and total cholesterol.^[7][8] However, these effects are not observed in longer trials.^[9][7] ALA may reduce the risk of heart arrhythmias, but has not been found to reduce blood pressure or the risk of cardiovascular events (e.g., heart attack, stroke).^[9] Additionally, ALA may reduce markers of inflammation including C-reactive protein and TNF-alpha; however, these effects are inconsistent and are mostly observed in people with higher baseline levels of these biomarkers.^[10][11] Some observational studies have suggested that higher reported intakes of ALA are associated with reduced all-cause and cardiovascular disease mortality,^[12][13] but this has not been found in randomized controlled trials (RCTs).^[9]

ALA is generally considered to be safe and well-tolerated; however, there is a lack of research reporting on adverse effects.

There are some important limitations to ALA research. Most trials provide ALA as foods or oils (e.g., flaxseed, walnut, canola, ALA-enriched-margarine), which means there are other bioactive compounds present, such as different fatty acids, fiber, vitamins and minerals, and polyphenols).^[7] These compounds could influence the observed effects and make it challenging to disentangle the effects of ALA from the food as a whole. Additionally, ALA is ubiquitous in the diet, and many clinical trials do not account for baseline intakes of ALA which could impact the observed effects (or lack thereof).

Animal models suggest that ALA might modulate blood lipid levels by reducing lipid synthesis while also stimulating lipid metabolism,^[3] and may reduce inflammation by reducing the production of inflammatory mediators through inhibition of nuclear factor kappa B (NF-kB). In theory, reductions in inflammation and blood lipids could be protective against cardiovascular disease, but a protective effect hasn’t been consistently found with ALA supplementation. ALA can also be metabolized into other bioactive compounds, such as oxylipins (e.g., eicosanoids), which are a diverse group of lipid mediators that have immune-modulating effects.^[14][15]